1. Field of the Invention
The present invention relates to a method for fault or failure analysis and a method for characterization of semiconductor devices. Particularly the present invention relates to a method for checking a leakage point with regard to a fault or failure with a leakage current in semiconductor components and relates to a measuring method for static characteristics and the like of devices.
2. Description of the Related Art
With regard to a fault or failure phenomenon of a semiconductor device with a leakage current, methods for checking the leakage point include hot electron analysis and an emission microscopic method (hereinafter referred to as an EMS method) which use a micro-luminescent phenomenon caused by a leakage current; and a liquid crystal analysis and a liquid crystal coating method which uses an exothermic reaction caused by the leakage current.
First, a resin packaging a semiconductor device is partially decomposed by a reagent such as fuming nitric acid, so that only a semiconductor chip located at the interior of the apparatus is exposed. This procedure does not change the electrical characteristics of the chip, because only the resin used for packaging the chip is removed.
Next, when the micro-luminescent phenomenon is used, a potential is applied to terminals of the semiconductor device. An abnormal luminescence occurs caused by the leakage current at the fault or failure point, so that the leakage point can be checked by observing the micro-luminescence. On the other hand, when the exothermic reaction caused by the leakage current is employed, a phase transition phenomenon of the liquid crystal applied on the chip occurring at a temperature above the transition point is used. Since the optical status of the liquid crystal changes at the leakage point, the leakage point can be checked by observing the point by a polarizing microscope.
However, the fault or failure analyses of a semiconductor device described above are carried out with difficulties in the case of a power-MOSFET in which a conductive wiring film covers substantially the entire surface of the chip. Furthermore, in a conventional semiconductor device, the leakage point may be located in an element immediately below an electrical power supply line having a relatively large linewidth of the conductive wiring film or a GND line in some cases. In such a case, the luminescence cannot be detected by the EMS method, because the conductive wiring film intercepts the light. In addition, with regard to the liquid crystal covering method, a significantly high current is required, resulting in the deterioration of the device.
Further, as a method of checking a leakage fault or failure of the semiconductor device covered with the conductive wiring film, an EMS observation is carried out from the rear surface of the chip by utilizing a phenomenon that the luminescent light caused by the leakage passes through a Si substrate. This method cannot, however, be applied to a semiconductor device in which electrodes are provided on the entire rear surface of the chip substrate such as a power-MOSFET.